The first thing to know about the 3D animated Legend of the Guardians: The Owls of Ga'Hoole, adapted from the first three of Kathryn Lasky's 2003 to 2008 series of 15 young-adult novels, is not to take any kid with a fear of heights. Fledgling barn owls still learning to fly light precariously onto branches that seem a mile off the ground, teetering and about to topple from what looks like an Empire State Building-scale drop. The dense woods and bald, craggy peaks rendered with a vaguely storybook glaze are ominous and filled with lethal dangers like a red-eyed Tasmanian devil, all mindless, pure shark instinct, dashing in for the kill when young dreamer Soren (voice of Jim Sturgess) and his rougher-hewn brother Kludd (Ryan Kwanten) find themselves on the forest floor. Their rescue by two scarred older owls who carry them off to who-knows-where seems like the beginnings of some ripping Robert Louis Stevenson adventure at first, with the rescuers' self-conscious bravado and comparisons of their scary-look faces seeming to signal a boys' adventure yarn of Runyonesque not-so-bad guys. Turns out that's far, far from the case.

You can't, of course, fault the books or the movie for turning out not to be that. But you do have to wonder why a PG rather than PG-13 movie heads instead into darkness straight out of Charles Dickens and Joseph Conrad, as our young heroes—one of whom quickly turns to the dark side, to the point of delivering his baby sister (Adrienne deFaria) into slavery—are plunged into a militaristic labor camp and turned into zombie-like slaves via a process called "moon blinking." This isn't based on a children's-book series, after all, but young-adult novels. PG? What was the MPAA thinking?

Stylized onscreen by director Zack Snyder, whose 300 and Watchmen were sumptuous banquets of color, texture, changing tempo and a sense of seeing something never seen before, Legend of the Guardians has the best-looking hooters outside Hooters. Barn owls, snowy owls, elf owls, burrowing owls, great horned owls and owls of every stripe and circumstance are rendered with feathery fidelity. And you couldn't swing an owl inside Oz’s National Institute of Dramatic Art without hitting some of the cream of Australia's actors who contribute voices here: Hugo Weaving, Sam Neill, Geoffrey Rush, Anthony LaPaglia, Abbie Cornish, David Wenhan…plus Brits Miriam Margolyes and Helen Mirren, who even at 65 makes the evil owls' queen effortlessly and rather disconcertingly seductive.

After an initially draggy opening, the movie springs into fast-paced flight, as Soren seeks to stop the Aryan-like "Pure Ones" from subjugating the owl world. Undertaking a quest for the fabled "Guardians" who live at the Great Tree across a mist-shrouded stretch of ocean, he finds a band of allies along the way, including the endearingly nervous and comical Digger (Wenham) and the wonderfully Falstaffian Twilight (LaPaglia).

But for all that comradeship and the movie's coming-of-age life lessons, there is still an emotional darkness that ripples outward from the hero's very name, Soren, as in Kierkegaard, who saw being and nothingness as the contradictory same and introduced to Europe the Nietzschean abyss. All this becomes more and more palpable as the movie soldiers on, filled with razor-winged bats, Freddy Krueger claws, graphic slashings and coal-blazing eyes peering from beneath war helmets forged amid hellfire sparks. Beautiful, horrible and not for young children, this is 300 with owls.